S-Space College of Engineering/Engineering Practice School (공과대학/대학원) Dept. of Material Science and Engineering (재료공학부) Theses (Ph.D. / Sc.D._재료공학부)
Anchoring Plasmonic Octahedral Au Nanoparticles for Solar Water Splitting Application
물분해 응용을 위한 팔면체 금나노입자 표면 기능화
- 공과대학 재료공학부
- Issue Date
- 서울대학교 대학원
- Plasmon; Localized surface plasmon; Plasmon enhanced solar water splitting; Octahedral gold nanoparticles; Catalytic hole transfer; Hot electron injection Resonant electron transfer; PEGylation; Thiolated PEG; (111) facet; Ligand exchange; FDTD simulation; Solar water splitting
- 학위논문 (박사)-- 서울대학교 대학원 : 공과대학 재료공학부, 2018. 2. 장호원.
- Due to their localized surface plasmon resonances in visible spectrum, noble metal nanostructures have been considered for improving the photoactivity of wide bandgap semiconductors. Improved photoactivity is attributed to localized surface plasmon relaxations such as direct electron injection and resonant energy transfer. However, the details on the plasmonic solar water splitting through near electromagnetic field enhancement have not been fully understood. The performance of plasmonic Au nanostructure/metal oxide heterointerface shows great promise in enhancing photoactivity, due to its ability to confine light to the small volume inside the semiconductor and modify the interfacial electronic band structure. Therefore, the shape control of Au nanoparticles (NPs) is crucial for moderate band gap semiconductors, because plasmonic resonance by interband excitations or intraband excitations overlaps above or below the absorption edge of semiconductors,
This thesis presents about plasmon enhanced photoelectrochemical water splitting, based on semiconductor photoanode in three main chapters. The first chapter focus on a plasmon enhanced photoelectrochemical water splitting for band-edge non-straddle semiconductor (mainly TiO2) by deprotonation method. The second chapter focus on a plasmon enhanced photoelectrochemical water splitting for band-edge straddle semiconductor (mainly BiVO4). The last chapter includes the high-coverage octahedral Au nanoparticle decoration method from ligand exchange via phase transfer. The high-coverage octahedral Au nanoparticle decorated BiVO4 film overcome theoretical efficiency.
At the first, I report that shape-controlled gold nanoparticles on wide bandgap semiconductors improve the water-splitting photoactivity of the semiconductors with over-bandgap photon energies compared to sub-bandgap photon energies. It is revealed that hot hole injection into the oxygen evolution reaction potential is the rate-limiting step in plasmonic solar water splitting. The proposed concept of photooxidation catalysts derived from an ensemble of gold nanoparticles having sharp vertices is applicable to various photocatalytic semiconductors and provides a theoretical framework to explore new efficient plasmonic photoelectrodes.
At the second, I firstly study the plasmonic effects of shape-controlled Au NPS on bismuth vanadate (BiVO4), and report a largely enhanced photoactivity of BiVO4 by introducing the octahedral Au NPs. The octahedral Au NPs/BiVO4 achieves 2.4 mA/cm2 at the 1.23 V vs. reversible hydrogen electrode, which is the 3-fold enhancement compared to BiVO4. It is the highest value among the previously reported plasmonic Au NPs/BiVO4. Improved photoactivity is attributed to the localized surface plasmon resonance
direct electron transfer (DET), plasmonic resonant energy transfer (PRET). The PRET can be stressed over DET when considering the moderate band gap semiconductor. Enhanced water oxidation induced by the shape-controlled Au NPs is applicable to moderate semiconductors, and shows a systematic study to explore new efficient plasmonic solar water splitting cells.
At the last, the essential benefit of introducing gold nanoparticles is an enhanced light energy conversion by generating plasmon. The plasmon decay induces various phenomena such as heat generation, near-field enhancement, hot electron injection, and resonance energy transfer. Shape-controlled octahedral gold nanoparticles having sharp vertices can maximize the efficiency of these processes. For practical plasmonic gold nanoparticle engineering, a high-coverage decoration method of octahedral gold nanoparticles comparable to physical vapor deposition on a semiconductor nanostructure is indispensable. However, the ligand exchange reaction to attach octahedral gold nanoparticles is limited in aqueous solution due to the inactivity of gold (111) surface by densely-packed cetyltrimethylammonium bilayer structure. Here, we report a controllable high coverage surface decoration method of octahedral gold nanoparticles on the targeted semiconductor nanostructures. The thiolated polyethylene glycol adsorption in gold (111) surface is achieved via phase transfer by ethanol-dichloromethane medium. In the application of solar water splitting, a high-coverage decoration of BiVO4 film resulted over the theoretical photocurrent. I expect that our results deliver an innovative platform for future plasmonic gold nanoparticle applications.